Glaucoma medication for altitude sickness

While sorting through some things this weekend, I found a little bag with five white pills in it. It’s glaucoma medicine, and it’s prescribed to me. I don’t have glaucoma, but I did visit the Himalayas in 2011.

Rapid ascent to high altitudes can cause altitude sickness, with nausea, headaches, and other symptoms that could make the whole trip unenjoyable. There is no logic or reason to who gets altitude sickness. Age, fitness, underlying conditions, travel experience – none of this matters. Altitude sickness appears to hit people at random, and the only way to know whether you’re susceptible is to go to high altitudes. The highest altitude I’d been was…Switzerland? Nevada? I’d been fine there, but those places have nothing on the Himalayas, which are about ten times higher, so I had no clue how I’d fare.

Because not many people travel from low altitudes to high altitudes, and not even all of these people get altitude sickness, there isn’t really a market for a specific over the counter drug to combat it. Luckily for travellers, an existing drug is quite good at preventing altitude sickness. That drug is Diamox, developed for glaucoma.

The active ingredient in Diamox is acetazolamide. It relieves pressure in the eyeballs (glaucoma) by inhibiting the enzyme carbonic anhydrase. This reduces the levels of bicarbonate, which in turn inhibits the productions of the liquid that builds up in the eye. Acetazolamide also increases the excretion of bicarbonate from the body via urine. Bicabonate is a base, and reducing its levels causes the blood to be more acidic. This is the mechanism that helps relieve altitude sickness: the acidic blood increases ventilation, and increases the amount of oxygen in the blood.

Travel clinics regularly give Diamox to travellers, but it’s not an officially approved drug for the purpose. So instead of a nice box, my Diamox are in a little plastic baggie – the universal packaging material for non-approved drugs of all kinds.

I was told I could take the pills before going up, but I could also start on the first day of ascent, if I was feeling nauseous, or just decide at that point not to take them if I thought I was going to be fine. I started my trip in Kathmandu, and going from England to Kathmandu was one of the biggest jumps in elevation we were doing on that trip. I was fine. A few days later, we flew to Lhasa, which is even higher. I was still fine. We gradually went higher each day, and I had my pills ready to take as soon as I felt sick, but I was fine the entire time.

I made it all the way up to Mount Everest Base Camp without having to take any of the pills, which is why I still have them. They haven’t reached their expiration date yet, but they will expire before I go to altitude again, and definitely before I’m old enough to get glaucoma. I’m keeping them as a trophy, as proof that I’m tough enough to go all the way to Mount Everest without getting altitude sickness.

Eva Amsen is a writer, science communicator and blogger. She has been writing about science and scientists in art/culture/life since 2005, both on this blog and for other sites and publications.
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